Blocking Facetime application

Blocking Apple's Facetime app can be problematic. The most effective way to block Facetime is to block the 'FACETIME' signature in Application Control > Signatures:

You can also block port 5223 in Config > Network > Filter Rules.  Facetime uses several ports: 53, 80, 443, 5223, and 16393-16472 (UDP), but blocking 5223 will prevent calls from going though.